Bonekamp S, Corona-Villalobos CP, Kamel IR .Oncologic Applications of diffusion-weighted MRI in the body
The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland 21287, USA. Journal of Magnetic Resonance Imaging
(Impact Factor: 3.21).
02/2012; 35(2):257-79. DOI: 10.1002/jmri.22786
Diffusion-weighted MRI (DWI) allows the detection of malignancies in the abdomen and pelvis. Lesion detection and characterization using DWI largely depends on the increased cellularity of solid or cystic lesions compared with the surrounding tissue. This increased cellularity leads results in restricted diffusion as indicated by reduction in the apparent diffusion coefficient (ADC). Low pretreatment ADC values of several malignancies have been shown to be predictive of better outcome. DWI can assess response to systemic or regional treatment of cancer at a cellular level and will therefore detect successful treatment earlier than anatomical measures. In this review, we provide a brief technical overview of DWI, discuss quantitative image analysis approaches, and review studies which have used DWI for the purpose of detection and characterization of malignancies as well as the early prediction of treatment response.
Available from: Patrick Bourguet
- "In biologic tissues barriers such as endothelium , cell membranes, components of the extracellular matrix and intracellular organelles restrict diffusion; increase or decrease in these barriers modifies the degree of water diffusion leading to a reduction or retention of MR signal. Tumour foci are visualised as increased signal-intensity on DW-MRI images with a corresponding decrease in the measured Apparent Diffusion Coefficient (ADC), which represents the rate of signal loss with increasing diffusion weighting . As the diffusion properties of bone metastases are significantly different to agematched normal marrow , DW-sequences are now almost routinely used as an adjunct to conventional T1- W images . "
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ABSTRACT: Assessment of the response to treatment of metastases is crucial in daily oncological practice and clinical trials. For soft tissue metastases, this is done using computed tomography (CT), Magnetic Resonance Imaging (MRI) or Positron Emission Tomography (PET) using validated response evaluation criteria. Bone metastases, which frequently represent the only site of metastases, are an exception in response assessment systems, because of the nature of the fixed bony defects, their complexity, which ranges from sclerotic to osteolytic and because of the lack of sensitivity, specificity and spatial resolution of the previously available bone imaging methods, mainly bone scintigraphy. Techniques such as MRI and PET are able to detect the early infiltration of the bone marrow by cancer, and to quantify this infiltration using morphologic images, quantitative parameters and functional approaches. This paper highlights the most recent developments of MRI and PET, showing how they enable early detection of bone lesions and monitoring of their response. It reviews current knowledge, puts the different techniques into perspective, in terms of indications, strengths, weaknesses and complementarity, and finally proposes recommendations for the choice of the most adequate imaging technique.
Available from: Subramaniyan Ramanathan
- "The reader is requested to refer to various articles available on principles, imaging parameters and pitfalls of diffusion imaging, as these are beyond the scope of our article [5, 6]. Malignant tumours are generally depicted as foci of increased intensity on DWI and decreased signal intensity on ADC images, because water diffusion is restricted in highly cellular tissues in malignant tumours [5, 7, 8]. However, blood, fat, abscesses, lymph nodes, and melanin can show restricted diffusion and can be resolved by referring to standard T1- and T2-weighted images . "
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Although rectal cancer is by far and large the most common pathology involving the rectum that needs imaging, there are many other important but less common pathological conditions affecting anorectal region. The objective of this pictorial review is to discuss the cross-sectional imaging features of less common anorectal and perirectal diseases.
Although a specific histological diagnosis cannot usually be made due to considerable overlap in the imaging appearances of anorectal diseases, this review illustrates the cross-sectional imaging findings with emphasis on magnetic resonance imaging (MRI) that can help in narrowing down the differentials to a reasonable extent.
• Variety of pathology exists in the anorectum apart from common rectal carcinoma
• Anorectal diseases present as non-specific wall thickening indistinguishable from rectal carcinoma
• Computed tomography (CT) and MRI can help in narrowing down the differentials, although often biopsy is warranted.
Available from: Thomas Schlosser
- "Hence, ADC values could be used to identify clinically significant more aggressive prostate cancers. In oncologic imaging, the ADC can be used as an indicator of therapeutic response during chemotherapy, as it has been reported that ADC values tend to rise under ongoing treatment , . This can be explained with a disintegration and decrease of tumor cells leading to an alleviation of water diffusion. "
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To characterize intermediate and high-risk prostate carcinomas with measurements of standardized uptake values (SUVs) and apparent diffusion coefficient (ADC) values by means of simultaneous [18F] choline PET/MRI.
Materials and Methods
35 patients with primary prostate cancer underwent simultaneous [18F] choline PET/MRI. From these, 21 patients with an intermediate and high risk constellation who were not under ongoing hormonal therapy were included. Altogether 32 tumor lesions with a focal uptake of [18F] choline could be identified. Average ADC values (ADCaver) minimum ADC values (ADCmin) as well as maximum and mean SUVs (SUVmax, SUVmean) of tumor lesions were assessed with volume-of-interest (VOI) and Region-of-interest (ROI) measurements. As a reference, also ADCaver, ADCmin and SUVmax and SUVmean of non-tumorous prostate tissue were measured. Statistical analysis comprised calculation of descriptive parameters and calculation of Pearson’s product moment correlations between ADC values and SUVs of tumor lesions.
Mean ADCaver and ADCmin of tumor lesions were 0.94±0.22×10−3 mm2/s and 0.65±0.21×10−3 mm2/s, respectively. Mean SUVmax and SUVmean of tumor lesions were 6.3±2.3 and 2.6±0.8, respectively. These values were in each case significantly different from the reference values (p<0.001). There was no significant correlation between the measured SUVs and ADC values (SUVmax vs. ADCaver: R = −0.24, p = 0.179; SUVmax vs. ADCmin: R = −0.03, p = 0.877; SUVmean vs. ADCaver: R = −0.27, p = 0.136; SUVmean vs. ADCmin: R = −0.08, p = 0.679).
Both SUVs and ADC values differ significantly between tumor lesions and healthy tissue. However, there is no significant correlation between these two parameters. This might be explained by the fact that SUVs and ADC values characterize different parts of tumor biology.
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